DESCRIPTION (provided by investigator): Sleep Disordered Breathing (SDB) is a common condition in the elderly population but its relationship to health in old age remains uncertain and its natural history is virtually unknown. The proposed longitudinal study will continue a previously initiated follow-up of a cohort of elderly subjects studied with physiologic sleep recordings (polysomnography). This unique group of 256 individuals, initially recruited and evaluated with in-lab polysomnography between 1974 and 1985 and followed prospectively since that time, is referred to as the Bay Area Sleep Cohort (BASC). A substantial number of BASC subjects already have undergone two occasions of polysomnographic measurement (n = 173), whereas as a smaller subgroup has been studied previously on three occasions (n = 76). Surviving BASC subjects (n = 137, X age = 81.2) will be re-recorded in a joint effort between investigators at Emory University in Atlanta, Georgia and SRI International of Menlo Park, California. These two institutions, and the Principal Investigator and Co-Principal Investigator, respectively, have a ten-year history of working on field studies of SDB in elderly populations in different geographic regions in the United States. The application requests funds to locate all surviving members of BASC as well as to: follow-up these individuals using current state-of-the-art ambulatory polysomnographic technology; perform comprehensive evaluations of health, including measures of neurobehavioral, pulmonary, and cardiovascular function among those surviving members; archive and summarize existing polysomnographic recordings; and to analyze data longitudinally by calculating each individual's rate of change in their characteristic levels of SDB. Individual differences in rates of change will be related to changes in neurobehavioral, pulmonary, and cardiovascular function over time. "Families" of regression lines will compare stage-specific rates to examine how changes in sleep architecture parallel development of SDB at follow-up. These results will allow elucidation of SDB as a potentially sensitive aging biomarker as well as characterizing how this index of physiologic age relates to other better recognized biomarkers of aging. The early establishment of this cohort and the absolute scarcity of information on population-based data on the progression of SDB present a unique opportunity to discover how human sleep may reflect fundamental alterations in aging processes.